Measures of Species Diversity



Species Accumulation Curves

  • Used to show when sampling is complete and all species have been identified
  • Quantifies the number of species found (y) per sampling effort (x).


N samples

Extrapolation Curves

Fit to data from an Accumulation curve to estimate how many species there might be.


N samples

Comparing Sampling Efforts

At which site would you expect to document more species?

  • Probably at Site 1, where sampling effort is greater.

How can we test whether site differences are meaningful?

We can rarefy our counts.

  • Rarefaction randomly selects a subset of observations from each site to equalize the sampling effort.
  • The resulting rarefaction curve can be used to compare species richness at the same level of sampling effort.


N samples

Species Diversity and Sampling Effort

Scales of Biodiversity

If funds were available to protect only one mountain range, which should be selected?

Region 2
the greatest gamma (total) diversity.

If funds were available to protect only one mountain, which should be selected?

Region 1
the greatest alpha (local) diversity.

If region 3 were selected for protection:

The relative priority of the individual mountains should then be judged based on the relative rarity of the assemblages.